1. Field of the Invention
The present invention generally relates to apparatuses and methods for measuring distances, and particularly, to an apparatus and a method using light to measure distances.
2. Description of Related Art
Distance measurements are used in various fields, such as engineering surveying, driving automobiles, etc. Electronic devices including optical elements, such as digital cameras, generally use lens to measure distances of objects to be photographed for correct focus. Some projectors also measure distances of screens to be projected on for auto focusing.
Conventionally, light pulses are used for measuring distances. A light source emits light pulses to an object to be measured. At the light source side, a light receiver is set to receive reflected light pulses. The light receiver converts the reflected light pulses into electric signals. The distance of the object to be measured can thus be calculated through the duration from the time that the light pulses are emitted to the time that the light pulses are received. Another method for measuring the distance is to calculate a phase difference between the emitted light pulses and the received light pulses. Such methods need rather accurate control and the calculation is rather complex.